not a lot of changes in them. thought a orange one with the buckle straps would be more age appropriate for the 75. the one in Brendon's 63 had the canvas tied to the frame. the only one like that I have seen
they offered the 3 colors at the same time. black, orange and the blue gray. the military used the black. but it was not exclusive to them. a lot of stuff has filtered back in that way. right now if I recall correctly you can get black, orange or maroon. but what I'm really keeping my eyes open for is a cotton mattress for the 53.
Ed,
Find me one in red, or maroon, and I will swap you the black one for it.
Correction. Serial number is 51111.